This invention relates to a needle, particularly for introducing a thread into the material to be sewn (generally referred to hereafter as "fabric") by means of a sewing machine
During sewing of a fabric, an "upper" thread is repeatedly introduced into the fabric by means of a needle which has an eye adjacent the needle point. Each time the needle is withdrawn, a loop is formed which is caught by a loop gripper and a "lower" thread is pulled through the loop. As a result, a seam is obtained which is composed of the upper and lower threads. To be able to pull the lower thread through the loop, the loop is caught by the loop gripper and is enlarged for pulling it around a bobbin containing the lower thread. For this purpose first the loop gripper pulls on the upper thread which thereafter is withdrawn through the needle eye. Consequently, the upper thread passes through the needle eye several times, resulting in substantial stresses to which the thread is exposed.
Further, sewing methods are known where the upper thread is introduced into or through the fabric without holding firmly the thread and the produced loop by a gripper during withdrawal of the needle. If during such an operation a loop is reliably formed, the thread has to be held by friction between the itself and the fabric.
U.S. Pat. No. 3,523,510 discloses a tufting needle for the manufacture of tufted carpeting. The needle serves for introducing a pile yarn through a backing fabric and to form loops with the pile yarn. For this purpose, the tufting needle has an approximately cylindrical blade which ends in a point. In the vicinity of the needle point a funnel-shaped eye is formed which is inclined to the central axis of the needle at approximately 30.degree.. An air channel provided in the tufting needle supplies pressurized air to the eye. Adjoining the eye on both oppositely located sides of the tufting needle shallow troughs are provided whose depth is less than the smallest diameter of the eye. Adjacent the eye the blade is cylindrical in the direction of its clamping location and is conical in the direction of the needle point. The loop formation is enhanced in such a needle by the effect of the pressurized air introduced into the eye. Other means for holding the thread loop are not disclosed in the above-noted U.S. Patent.
A further tufting needle is disclosed in Published European Application 187 925. The tufting needle disclosed therein has a tubular base body which is obliquely cut for forming a point. At the side opposite the oblique face the tubular base body is also open so that a thread running through the open inner space may exit at the obliquely arranged outlet surface of the tubular base body. The eye formed in this manner has an oval cross-sectional shape which changes along the eye because of a deformation imparted on the tubular base body. On that side of the tubular base body which is opposite its open side, the tubular base body is flattened so that a bay or hollow wedge is formed.
A further tufting needle is described in German Patent No. 2,834,738. The needle disclosed therein has a needle base body provided with a flat cross-sectional configuration which, according to one embodiment, extends essentially unchanged to the needle eye oriented transversely to the longitudinal axis of the needle and has lengthwise an oval shape. A trough leads to the eye; the trough is significantly shallower than the height of the thread. The length of the eye in this embodiment is approximately the same size as the mouth of the eye at the two opposite needle sides.
According to another embodiment disclosed in German Patent No. 2,834,738 a tufting needle has an approximately spoon-shaped head. A thread trough extending along the needle blade has a depth which is less than the thread thickness and substantially less than the width of the eye. The eye is oval and extends transversely through the tufting needle. On that side which is opposite the thread trough an outwardly bent portion is provided in the region of the eye and in an adjoining blade zone.
Similar tufting needles are shown in German Patent No. 3,002,345, as well as U.S. Pat. Nos. 4,233,917 and 4,502,403.
German Offenlegungsschrift (application published without examination) 2,412,062 discloses a sewing needle configured to cooperate with a thread gripper. The sewing needle serves to push the upper thread through the fabric, and the loop which is being formed is then held by the thread gripper and is enlarged. The sewing needle has a blade having a thread trough whose depth is slightly greater than the smallest diameter of the eye so that the thread runs entirely within the trough. The eye extends along an arcuate path transversely through the needle and flares in a funnel-shaped manner. The shape of the eye is oval in cross-section. A depressed face is located on that side of the eye which is remote from the needle point and which faces away from the thread trough and immediately adjoins the needle eye. The depressed face is provided for the hook or gripper which cooperates with the needle.